Parent Company (Franklin Financial Services Corporation) Financial Information (Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 52,957	$ 58,603	$ 36,665	$ 39,166
Other assets	8,545	6,930
Total assets	1,209,587	1,179,813
Other Liabilities	8,562	17,488
Total liabilities	1,091,191	1,064,669
Shareholders' equity	118,396	115,144	116,493	111,376
Total liabilities and shareholders' equity	1,209,587	1,179,813
Franklin Financial Services Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	108	250	$ 851	$ 300
Investment securities	374	365
Equity investment in subsidiaries	118,027	114,387
Other assets		184
Total assets	118,509	115,186
Other Liabilities	113	42
Total liabilities	113	42
Shareholders' equity	118,396	115,144
Total liabilities and shareholders' equity	$ 118,509	$ 115,186